A recent focus of our research has been the molecular characterization of the catalase peroxidase (katG) protein that has been shown to be associated with mycobacterium virulence as well as sensitivity to INH. Using site-directed mutagenesiis, we have established that specific katG mutations can cause a reduction in enzymatic activity resulting in resistance to INH. We have also established a system for evaluating the effort of specific katG mutations on the functional oligomerization of katG. We have shown the same katG mutations are transdominant in this system. In addition, we have been evluating the role of the ahpC gene in resistance to INH. Our in vitro studies adn our evaluation of 60 clinical isolates for ahpC mutations suggests that ahpC plays no role in the INH resistance. Finally, we are utilizing our experience in identifying mutations in drug target genes to develop rapid assays, based on PNA-technology, to detect drug-resistant organisms. These PNA methods, if successful, will greatly accelarate and improve detection of drug resistant organisms.